Based on the theory of extension, in order to deal with the problems raised by highlight of the cultural design elements of Qinhuai Colored Lantern in industrial product design and the need for its evaluation, the work aims to transform the cultural characteristics of Qinhuai Colored Lantern, an intangible cultural heritage, into cultural elements in a formal way. Extension semantics and graphic thinking are adopted in the design process. The gradual convergent evaluation of the diagrammatic semantics of cultural features provides strong support for design practice. At the same time, the graphic thinking is used to transform the meaning of graphics into the meaning of images, and the degree of relation between the meaning of graphics and cultural connotation is used as the semantic set to judge the cultural characteristics of graphics. The abstract cultural characteristics of intangible cultural heritage are transformed into quantifiable cultural elements, which provides a cultural reference for product design. By combining the theory of extension semantics and transforming tacit knowledge into primitive elements that can be expressed and evaluated rationally, the practical feasibility of design is obtained. Based on the feature analysis method of graphic thinking, the focused evaluation of the graphic semantics of cultural features is realized, which, combined with the design practice of modern lamps, provides reference for the design method of the intangible cultural heritage products of Qinhuai Colored Lantern.